About r/Astronomy
In its own words:
The amateur hobby of humanity since the dawn of time and scientific study of celestial objects.
The community was created on Mar 28, 2008, which makes it 18 years old. Since Oct 19, 2026, it has gained 2,539 subscribers (+0.08%). Among the 11 communities on our space and astronomy list it is number 4 by size.
What sets r/Astronomy apart
r/Astronomy is far more image-driven than most big subreddits: 46% of its recent posts are images, against a median of 9% across the Top 100. People mostly look and upvote here rather than comment — about 6.5 comments per post, against 16.2 for a typical large subreddit. Its rhythm is strongly tied to time zones: the busiest hour (15:00 UTC) sees about 8.0× as many posts as the quietest (07:00 UTC).
Subscriber growth
Between Sep 19, 2026 and Oct 29, 2026, r/Astronomy grew from 3,147,383 to 3,155,879 subscribers (+8.5K, +0.27%). That is about 212 new members per day. The chart uses our weekly snapshots (8 so far), so it gets longer every week.
What r/Astronomy talks about
Across 186 recent posts (Oct 21–Oct 28), the words that come up most are “nebula”, “moon”, “solar”, “galaxy” and “star”. Other frequent themes are tonight, captured, andromeda, sun, orion and ngc. Recurring phrases include “black hole”, “andromeda galaxy”, “orion nebula” and “solar system”. By format, 46% are images, 23% are text posts and 17% are galleries.
Popular post flairs: Astrophotography (OC) (97), Discussion: [Topic] (23), Astro Research (22), Other: [Topic] (22), Astro Art (OC) (2), Discussion: SGP4 3D map (1).
Activity and best time to post
r/Astronomy gets about 25 new posts a day. The public archive holds 158,404 posts and 1,026,721 comments in total, about 6.5 comments per post. Last week the busiest day was Friday (33 posts) and the quietest was Wednesday (21). Posting peaks around 15:00 UTC and is lowest around 07:00 UTC.
Rules of r/Astronomy
The moderators of r/Astronomy list 11 rules. In short:
- Pictures & Videos
- Object Identification
- Questions
- Telescope Help
- Content
- Behavior
- Sources
- Repetition & Relevance
- Misinformation & Pseudoscience
- Minimum Karma
How to join
Open reddit.com/r/Astronomy and press “Join”. Read the community rules in the sidebar before you post: every subreddit is run by its own volunteer moderators.
Frequently asked questions
How big is r/Astronomy?
r/Astronomy has 3,155,879 subscribers, which makes it the #333 safe-for-work subreddit in the SubMouse ranking. It added 8,496 members between Sep 19, 2026 and Oct 29, 2026.
How old is r/Astronomy?
r/Astronomy was created on Mar 28, 2008, so it has been around for 18 years.
How active is r/Astronomy?
Very active: r/Astronomy gets about 25 new posts a day (average of the last four weeks). Over its lifetime the archive counts 158,404 posts and 1,026,721 comments. In a sample of 186 recent posts we counted 147 different authors.
When is r/Astronomy most active?
Based on post counts from Oct 22, 2026 to Oct 28, 2026, the busiest day was Friday and the quietest Wednesday, and most posts arrive around 15:00 UTC, with the fewest around 07:00 UTC. More posts also means more competition, so a quieter hour can help a post get noticed.
What is r/Astronomy about?
The community describes itself as: “The amateur hobby of humanity since the dawn of time and scientific study of celestial objects.” Recent post titles often mention nebula, moon, solar, galaxy and star. Most posts are images (46%).
Is r/Astronomy safe for work?
Yes. Reddit does not mark r/Astronomy as an 18+ (NSFW) community. SubMouse lists safe-for-work subreddits only.
How do I post on r/Astronomy?
Join the community on Reddit first, then use “Create post”. r/Astronomy accepts both text and link posts, with images, videos and galleries enabled. It has 11 posted rules, starting with: “Pictures & Videos”; “Object Identification”; “Questions”. Moderators remove posts that break the rules, so read them in the sidebar before posting.
Which communities are like r/Astronomy?
Communities with similar topics include r/science (34.6M), r/astrophotography (2.6M), r/Futurology (21.7M), r/space (28M) and r/memes (36.1M).
Stats from public data (data updated Oct 29, 2026; activity, rules and archive totals via the Arctic Shift archive, Oct 30, 2026). Point and comment counts are archive snapshots and can be lower than on Reddit today. SubMouse is an independent directory and is not affiliated with Reddit or the moderators of r/Astronomy.